The precipitation of copper from a copper solution (prepared, for example, by leaching a mine or copper oxide dump with a weak inorganic acid, such as sulfuric or hydrochloric acid) takes place in the presence of iron on account of the electromotive difference between copper and iron according to the known exemplary reaction equations: EQU CuSO.sub.4 + Fe .fwdarw. FeSO.sub.4 + Cu; EQU CuCl.sub.2 + Fe .fwdarw. FeCl.sub.2 + Cu; or EQU 2 CuCl + Fe .fwdarw. FeCl.sub.2 + 2 Cu.
The precipitated copper is termed "cement copper". The iron ordinarily is added to such solution in the form of sheet-iron scrap, cast iron bars, or iron sponge. In achieving precipitation, it is important that the surface of the iron be constantly kept clean; that is, the precipitated copper should be constantly separated from the iron, so that further copper may precipitate thereon. Towards this end, the iron pieces need to be kept constantly in motion.
In the case of the known precipitation techniques, this end has been sought by various means. Thus, in one apparatus, an agitator device is installed in the precipitation container. In another apparatus, the iron is automatically introduced, or rather introduced into, automatically moved baskets or rockers made of copper or wood. In another apparatus, the precipitation is accomplished in rotating, acid proof lined iron drums. When, in such last apparatus, a certain acceleration of the course of the reaction can be attained, then, for example, with a precipitation drum of approximately 30 m.sup.3 of utilizable volume, it always takes about 1 hour or more until the copper is precipitated out to a desired copper residue content below about, 0.1 g/l in the decopperized solution, which is a convenient upper level in the cement copper production field for copper in decopperized solution, as those skilled in the art appreciate.